Many transponders in close proximity

I do not know what radar band ATC uses, but couldn't one suspend a
metalic reflector like sailboats use to provide a radar return? Of
course, space would be consideration depending on the glider model (see
http://www.tri-lens.com/trilensweb12002002.htm)

... Incidentally, we (USAF) did tests with fibreglas gliders to see if
we could "see" them with ATC radars.. you typically could not unless
they increased their power above the rated power they were authorized
at the time... yet, if we put wadded up tin foil (Reynolds Aluminum
wrap) in the wings, they showed up like gang busters.

Jettester (UP)

Ya I'm pretty uncertain now re the take home message for those of us with
mode C installed already. I thought that it was a given that traffic with
TCAS were seeing me and that center/approach could also and vector traffic
around me. After this thread I 'm not feeling froggy about any of this. In
Phoenix and most other places I fly I have been squawking 1200 (Ely,
Moriarty) but are you guys saying that I will be ignored by ground radar due
to filtering for airspeed and by TCAS for 1200???? Glad I spent the $2000.
It all seems inane to me that we go to the effort to be seen and our reward
is being "filtered out" because some moron thinks we aren't a real threat.

Casey Lenox
KC
Phoenix

Kilo Charlie wrote:
Ya I'm pretty uncertain now re the take home message for those of us with
mode C installed already. I thought that it was a given that traffic with
TCAS were seeing me and that center/approach could also and vector traffic
around me. After this thread I 'm not feeling froggy about any of this. In
Phoenix and most other places I fly I have been squawking 1200 (Ely,
Moriarty) but are you guys saying that I will be ignored by ground radar due
to filtering for airspeed and by TCAS for 1200???? Glad I spent the $2000.
It all seems inane to me that we go to the effort to be seen and our reward
is being "filtered out" because some moron thinks we aren't a real threat.

You aren't being filtered out by airspeed or code. Read the posting by
Billy Hill. Your transponder is being seen by ATC, the airliner TCAS,
and everyone with a TPAS unit, so I think your $2000 was a good value
(that's what my Becker cost me, too). We still have to worry about all
the other gliders (even those with a transponder, because I don't have a
TPAS unit yet), and some/many of the small airplanes, too.


--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

www.motorglider.org - Download "A Guide to Self-launching Sailplane
Operation"

You aren't being filtered out by airspeed or code. Read the posting by
Billy Hill. Your transponder is being seen by ATC, the airliner TCAS, and
everyone with a TPAS unit, so I think your $2000 was a good value (that's
what my Becker cost me, too). We still have to worry about all the other
gliders (even those with a transponder, because I don't have a TPAS unit
yet), and some/many of the small airplanes, too.

Eric Greenwell - Washington State, USA

Hmm.....well maybe you missed this above from jettester Eric or he's
incorrect.....

Tom;
I am a FAA Test Pilot who is authorized to test Transponders in new
aircraft... I do this for a living. I also was qualified as a Hawker
800XP test pilot.

Bottom Line - Transponders are NOT the answer! Try putting one of
these new LED Strobe Lights on the top of your Fin instead.

#1. Transponders would not solve the mid air problem unless you were
the only one in close proximity to the attacking aircraft. Typically,
they set MTI (moving target indicator) to above 60K or higher
(especially if near a large amount of highway ground traffic), so once
you start thermalling they lose you unless you are given a discrete
squawk other than 1200 (for non participating VFR Traffic)

#2. If multiple gliders (or aircraft) are in the vicinity all
squawking 1200, ATC could not tell one from the other. Mode C (if you
have it) reports altitude, yet if the climb or descent rate is large
(let's say greater than 1500fpm) their equipment typically faults you
off the scope and does not report your altitude. Once again unless you
are given a discrete squawk other than 1200 (VFR traffic).

I also have a Becker and will continue to believe that its better than
nothing......

KC

Kilo Charlie wrote:

Hmm.....well maybe you missed this above from jettester Eric or he's
incorrect.....


Mode C (if you
have it) reports altitude, yet if the climb or descent rate is large
(let's say greater than 1500fpm) their equipment typically faults you
off the scope and does not report your altitude.

So, the aircraft climbing or descending at a high rate are the ones
they do NOT want to know about? This had better be wrong.

I suspect jettester's info may also be a little out of date. When did
he say he hung up his spurs?


Jack

Kilo Charlie wrote:
After this thread I 'm not feeling froggy about any of this. In
Phoenix and most other places I fly I have been squawking 1200 (Ely,
Moriarty) but are you guys saying that I will be ignored by ground radar due
to filtering for airspeed and by TCAS for 1200???? Glad I spent the $2000.
It all seems inane to me that we go to the effort to be seen and our reward
is being "filtered out" because some moron thinks we aren't a real threat.


The money you spent on a transponder was well spent. Now you need to
save up and buy a better bull**** filter!


Andy

5Z wrote:
With all this discussion going on now, maybe someone with some
knowledge or experience could enlighten us on the consequences of 10 or
more sailplanes in a tight gaglge all squawking the same info. Will
ATC see them all? Or will interference and/or filtering software at
ATC make some or all of them invisible?

Will TCAS be able to make sense of all these close together
transponders?


Tom,

The info included in this ref may be more reliable than some of the
postings here.

http://www.nak.no/flynytt/download/TCAS_II_V7.pdf

I'll check at work to find out what the latest version of the MOPS is.

Andy

Kilo Charlie wrote:
You aren't being filtered out by airspeed or code. Read the posting by
Billy Hill. Your transponder is being seen by ATC, the airliner TCAS, and
everyone with a TPAS unit, so I think your $2000 was a good value (that's
what my Becker cost me, too). We still have to worry about all the other
gliders (even those with a transponder, because I don't have a TPAS unit
yet), and some/many of the small airplanes, too.

Eric Greenwell - Washington State, USA

Hmm.....well maybe you missed this above from jettester Eric or he's
incorrect.....

Tom;
I am a FAA Test Pilot who is authorized to test Transponders in new
aircraft... I do this for a living. I also was qualified as a Hawker
800XP test pilot.

Bottom Line - Transponders are NOT the answer! Try putting one of
these new LED Strobe Lights on the top of your Fin instead.

#1. Transponders would not solve the mid air problem unless you were
the only one in close proximity to the attacking aircraft. Typically,
they set MTI (moving target indicator) to above 60K or higher
(especially if near a large amount of highway ground traffic), so once
you start thermalling they lose you unless you are given a discrete
squawk other than 1200 (for non participating VFR Traffic)

#2. If multiple gliders (or aircraft) are in the vicinity all
squawking 1200, ATC could not tell one from the other. Mode C (if you
have it) reports altitude, yet if the climb or descent rate is large
(let's say greater than 1500fpm) their equipment typically faults you
off the scope and does not report your altitude. Once again unless you
are given a discrete squawk other than 1200 (VFR traffic).

I also have a Becker and will continue to believe that its better than
nothing......

I saw jettester's posting, and I think he is wrong, based on my
information from other pilots and ATC people over the last few years.
For example, I don't think ATC has any problem distinguishing a
transponder from ground returns, regardless of the transponder's speed,
so the "MTI" comment doesn't apply. Perhaps jettester's experience is
outdated or perhaps the testing he did involved procedures that are not
normally used by ATC - I don't know.

Also, TCAS is designed to handle multiple targets, and ATC can determine
the location of transponders even if they close to each other. ATC may
not be able to get a reliable altitudes or code readings in that case,
but they know where the group is, and they are not going to let an
aircraft in contact with them fly into a swarm of aircraft.

Here is what Billy Hill posted (in part) on Aug 31 (pilots should also
read his article in the July 2006 Soaring magazine):

"Each controller is required by virtue of the ATC handbook, (7110.65 and
the management handbook 7110.3), to display ALL transponder equipped
aircraft. What the controller does have the option to do is adjust the
filter limits at his scope to exclude the encoded altitude of aircraft
which are not in his assigned airspace.
Had the transponder been turned on by the pilot involved in the
mid-air, the jet would have seen the glider on it's TCAS, and ATC
would have been issuing the glider as traffic to the jet. In the Reno
area, most glider pilots are squawking an non discrete code which
indicates to ATC that they are a glider."

People that have experimented with strobe lights have been disappointed,
because they don't help much in sunny conditions. I don't know if LED
strobes are more visible than the glass bulb type, but they do use less
current.

Enjoy your Becker - it's a far better solution than indicated by jettester.

--
Change "netto" to "net" to email me directly

Eric Greenwell - Washington State, USA

"Transponders in Sailplanes" on the Soaring Safety Foundation website
www.soaringsafety.org/prevention/articles.html

"A Guide to Self-launching Sailplane Operation" at www.motorglider.org

That doesn't provide altitude data, and the radar return would potentially
be filtered out as ground traffic due to the slow speeds involved.

Mike Schumann

"James D'Andrea" wrote in message
ps.com...
I do not know what radar band ATC uses, but couldn't one suspend a
metalic reflector like sailboats use to provide a radar return? Of
course, space would be consideration depending on the glider model (see
http://www.tri-lens.com/trilensweb12002002.htm)

... Incidentally, we (USAF) did tests with fibreglas gliders to see if
we could "see" them with ATC radars.. you typically could not unless
they increased their power above the rated power they were authorized
at the time... yet, if we put wadded up tin foil (Reynolds Aluminum
wrap) in the wings, they showed up like gang busters.

Jettester (UP)

588 wrote:
Kilo Charlie wrote:

Hmm.....well maybe you missed this above from jettester Eric or he's
incorrect.....


Mode C (if you
have it) reports altitude, yet if the climb or descent rate is large
(let's say greater than 1500fpm) their equipment typically faults you
off the scope and does not report your altitude.

So, the aircraft climbing or descending at a high rate are the ones
they do NOT want to know about? This had better be wrong.

I suspect jettester's info may also be a little out of date. When did
he say he hung up his spurs?


Jack

Sorry to all: I've been gone away from my computer for the holiday!
(was soaring !)

Wow, I was trying to clear up a number of misconceptions that people
typically have concerning Transponders. Did not mean to stir up a
hornets nest. Billy Hill is telling the truth also... so don't
misconstrue my remarks.

It depends on the radar you have in your area. whether you have 'line
of sight' with the glider and transponder whether the controller can
"see" your transponder. This is a continuation of my previous comments.

#7. My comments are reflective of "current" equipment used by ATC and
probably more current transponders than any of you can afford. Not
much has changed in the last 18yrs. Yet, I confirmed my previous
statements with the ATC supervisor here in Wichita as being correct.

#8. If two or more of you are operating on the same squawk code, and
end up with converging tracks or converging altitudes (if Mode C
equipped), you WILL set off ATC's traffic warnings (unless they turn
them off for all other traffic in your/their vicinity).

#9. Transponders are a good thing to have if ATC can "see" you, and
their participating traffic has TCAS.. it will "point" you out to that
traffic. TCAS uses the ATC radar to relay your transponder code and
altitude (if Mode C equipped) to that traffic.

#10. I spoke truthfully about their (ATC) not seeing you if climbing
too rapidly (or descending). It may X'out your info on their scope as
well as your altitude.

#11. A transponder may have helped the Hawker to receive a TCAS warning
if ATC could "see" the glider transponder (line of sight), Mode C would
have reported its altitude, and MTI did not filter because the glider
was not circling. I confirmed that MTI is set 65K in this area.

Jettester (UP)